1. Field of the Invention
The present invention relates to a multi type air conditioner and its control method, and more particularly, to a multi type air conditioner and its control method capable of improving heating operation efficiency by minimizing the flow resistance of a refrigerant when all operating indoor units are in a heating operation mode and of improving cooling efficiency by preventing an accumulation of a liquefied refrigerant in a high pressure pipe when all operating indoor units are in a cooling operation mode.
2. Description of the Conventional Art
In general, a multi type air conditioner includes several indoor units such that some perform heating and others perform cooling.
FIG. 1 is a construction view of the multi type air conditioner in accordance with the conventional art.
The multi type air conditioner in accordance with the conventional art includes an outdoor unit 102 heat-exchanged with the outdoor air, a plurality of indoor units 104 heat-exchanged with the indoor air and performing cooling and heating operation, and a distributor 106 disposed between the outdoor unit 102 and the indoor units 104 and properly distributing a refrigerant of the outdoor unit 102 to the indoor units 104.
The outdoor unit 102 includes a plurality of outdoor heat exchangers 108 heat-exchanged with the outdoor air, a four-way valve 110 switching the flow of a refrigerant in a forward or reverse direction, an outdoor expansion valve 122 disposed at a refrigerant pipe 120 connected between the outdoor heat exchanger 108 and the indoor unit 104, for changing a refrigerant to a low-temperature low-pressure refrigerant, a plurality of compressors 130 compressing the refrigerant to a high-temperature high-pressure refrigerant, and an accumulator 132 connected to an intake side of the compressors 130, dividing a refrigerant into a gas and a liquid and supplying a gaseous refrigerant to the compressor.
A blower fan 134 for blowing the outdoor air for heat exchange to the outdoor heat exchangers 108 is installed at one side of the outdoor heat exchanger 108, and a bypass flow path 126 provided with the check valve 124 is installed at the refrigerant pipe 120 where the outdoor expansion valve 122 is installed.
The indoor unit 104 includes a plurality of indoor heat exchangers 112 heat-exchanged with the indoor air, and an indoor expansion valve 114 installed at one side of the indoor heat exchanger 112.
The distributor 106 includes a high pressure pipe 140 connected to a discharge side of the compressors 130, first distribution pipes 144 diverged from the high pressure pipe to each indoor unit 104, a low pressure pipe 142 connected to an intake side of the compressors 130, second distribution pipes 146 diverged from the low pressure pipe 142 to the plurality of indoor units 104, first two-way valves 150 respectively installed at the first distribution pipes 144 and opening and closing the first distribution pipes 144, and second two-way valves 152 respectively installed at the second distribution pipes 146 and opening and closing the second distribution pipes 146.
Third distribution pipes 148 are diverged from the refrigerant pipe 120 connected to the outdoor heat exchanger 108 and are connected to the indoor heat exchanger 112.
Here, a large-diameter pipe having the biggest diameter is used as the low pressure pipe 142, and a middle-diameter pipe having a diameter smaller than that of the low pressure pipe 142 is used as the high pressure pipe 140, and a small-diameter pipe having a diameter smaller than that of the high pressure pipe 140 is used as the refrigerant pipe 120.
The operation of the air conditioner constructed in the aforementioned manner in accordance with the conventional art will now be described. As shown in FIG. 1, if all of operating indoor units 104 are operated for heating, the four-way valve 110 is controlled to connect the outdoor heat exchanger 108 with the intake side of the compressors 130, the first two-way valves 150 are all turned ON to open the high pressure pipe 140, and the second two-way valves are turned OFF to close the low pressure pipe 142.
In such a state, when the compressors 130 are operated, a refrigerant compressed by the compressors 130 flows along the high pressure pipe 140 having a middle diameter and is distributed to each indoor unit 104 by the first distribution pipe 144. The refrigerant supplied to each of the indoor units 104 is heat-exchanged with the indoor air to perform heating while passing through the indoor heat exchanger 112, and the refrigerant discharged from the indoor heat exchanger 112 flows along the refrigerant pipe 120 and is decompressed and expanded while passing through the outdoor expansion valve 122. Then, the refrigerant is introduced into the outdoor heat exchanger 108, is heat-exchanged with the outdoor air therein, and then is introduced to the compressors 130 via the four-way valve 110.
However, the air conditioner in accordance with the conventional art has the following problems.
If all of the operating indoor units are operated for heating, flow resistance occurs while a refrigerant passes through the high pressure pipe having a middle diameter because the refrigerant compressed in the compressors are supplied to each indoor unit through the high pressure pipe, which causes deterioration of the heating capacity and heating efficiency.
As shown in FIG. 2, if all of the operating indoor units 104 are operated for cooling, the first two-way valves 150 are turned OFF, and the second two-way valves 152 are turned ON. If the compressors 130 are driven in such a state, a refrigerant compressed by the compressors 130 are condensed while passing through the outdoor heat exchanger 108 and is supplied to each indoor unit 104 through the refrigerant pipe 120 and each third distribution pipe 148. The refrigerant supplied to the indoor unit 104 is decompressed and expanded while passing through the indoor expansion valve 114, and then, the refrigerant is supplied to the indoor heat exchanger 112. Having passed through the indoor heat exchanger 112, the refrigerant is heat-exchanged with the indoor air and performs cooling. The refrigerant having passed through the indoor heat exchanger 112 is introduced to the compressors 130 through the second distribution pipe 146 and the low pressure pipe 142 which are opened as the second two-way valves 152 are turned ON.
As mentioned above, because the first two-way valves 150 is turned OFF and thus, the high pressure pipe 140 is closed when all of the operating indoor unit 104 are operated for cooling, a portion of a high-temperature high-pressure refrigerant compressed in the compressors 130 fills in the high pressure pipe 140. Accordingly, condensation of the refrigerant occurs within the high pressure pipe 140, and thus a liquefied refrigerant is accumulated in the high pressure pipe 140, which causes a shortage of a circulating refrigerant and deterioration of cooling performance.
Particularly, if the high pressure pipe 140 becomes long because of a long distance between the outdoor unit 104 and the distributor 106, quite a large amount of liquefied refrigerant is accumulated within the high pressure pipe 140, which worsens the shortage of a circulating refrigerant and causes damage to the compressors 130 for lack of oil.